1. Field of the Invention
The present invention relates to carrier class switches, and in particular, a method and apparatus for providing high density differential services for voice over packet network applications in an integrated carrier-class switching platform.
2. Description of the Related Art
Since the development of the telephone, many different technologies for providing voice (and, more recently, fax and video) communications between two or more remotely situated persons have been developed.
In a basic telephone circuit-mode call (sometimes called “plain old telephone service” or “POTS”), the communications pathway (i.e. a circuit) between two users (102 and 104 in FIG. 1) over the public switched telephone network (PSTN 106) is fixed for the duration of the call and is not shared by other users. Although several users may share one physical line, typically by use of frequency division multiplexing, only one user is assigned to a single voiceband channel at any given time.
In circuit mode, a connection is obtained by establishing a fixed pathway through the network. The route is established after the calling party initiates the call setup procedure by telling the network the address of the called party, i.e., after the user dials the telephone number.
The temporary connection between the parties through the network exists for the duration of the telephone call. During that period, the circuit is equivalent to a physical pair of wires connecting the two users. The physical circuit connection is dedicated to this call and is not shared by other users.
The signaling protocol for such circuit-mode calls is simple. Users signal their desire to place a call by physically lifting the telephone receiver from the switchhook. This places an electrical short on the line, allowing current to flow from the central office (108, 110), where it passes through the winding of a relay in a circuit switch (112, 114). The relay operates and the network “knows” that the user wants to place a call. The network, in turn, transmits a dial tone to the user as a signal that it is ready to receive the called party's number, which the calling party transmits to the network either as a series of dial pulses or tones. The network then determines the physical pathway to the called party and “rings” the called party's telephone. When the called party picks up, the connection is established and exists for the duration of the call.
Telephone service using ISDN has recently become popular, particularly for medium to large sized businesses. Although ISDN uses an out-band signaling protocol such as SS7 (as opposed to the in-band signaling used by POTS wherein the same wire that is used during the call is used by the network to set up and disconnect the call), telephone calls placed via ISDN also use the PSTN 106 and are circuit-mode, though the carrier must provide SS7 functionality (116, 118) in addition to conventional PSTN functionality.
More recently, packet-switched networks have proliferated, led by the popularity of the Internet and other public and private networks. However, because fixed and exclusive “connections” between users communicating via packet-switched networks are not possible because of their design for best-effort traffic only, they have not been thought suitable for carrying voice calls. Nevertheless, many standards have been developed for providing voice-over-the-network (VON). These include voice over IP networks (VoIP), voice over ATM networks (VoATM) and voice over frame relay networks (VoFR). Along with such standards, signaling protocols have been developed for setting up voice calls (e.g. H.323 for VoIP).
Confronted with these burgeoning standards, conventional service carriers have scrambled to keep up. Because supporting each new standard can require a significant outlay in expense and infrastructure, typically, such carriers can provide support for only selected standards. For example, a carrier might choose to support VoIP by providing an IP gateway (120, 122). However, current VoIP gateways can only support a small number of voice ports (typically, a maximum of 96 ports) using a centralized processing scheme. Moreover, current VoIP gateways introduce increased voice latency, thereby reducing the usefulness of the service.
Furthermore, such VoIP gateways can only perform TDM to IP packet over Ethernet conversion, which provides only a signal path VON. They can not perform conversions to other media types such as ATM or FR, and therefore they can't provide differential VON services. Relatedly, conventional VoIP gateways do not support functionality for relaying between the various signaling protocols (e.g. SS7 to H.323). The ability to convert between different types of VON services (i.e. differential or “multipath” VON) in a single switching platform would be particularly useful, for example, for allowing users with any type of voice service to communicate with users having any other type of voice service. Moreover, such conversion functionality would also permit voice services customers to have established service profiles indicating their willingness to pay for more quality of service or preference for more value. Individual incoming or outgoing calls from such customers could then be treated according to their service profiles, in addition to the availability of system resources and their instantaneous cost or capacity.
Accordingly, there remains a need in the art for an integrated switching apparatus that solves the above-mentioned problems. The present invention fulfills this need.